Cash Isa to Shares ISA - would like to shelter existing non isa shareholdings

If I convert a Cash ISa to Shares ISA - what are the rules for sheltering existing shareholdings in this ISA. Obiously I declare shares I sell for capital gains -but are there any rules as to when share should be sold and bought. Can I buy shares for ISA and then sell at different dates afterwards. Or do I have to buy then sell within certain time limits. Thank you.

Hi Tessa,
You can move the contents of a cash ISA into a stocks and shares ISA without losing any of your £20000 allowance.
Have a look at the guidance here:
Individual Savings Accounts (ISAs)
Thank you. 
 

Many thanks. Can I shelter an existing holding of shares within this ISA - and if so, are there any rules on dates of purchase and sale of these shares.

Hi ,
 

As long as you have not exceeded the 20k input each year, yes. There is no time limits on buying/selling  . Thank you .